CREATE TABLE UserCoupons (
UserID INT NOT NULL ,
CouponID INT NOT NULL,
Quantity INT NOT NULL,
PRIMARY KEY(UserID, CouponID)
)  

ALTER TABLE UserCoupons
ADD CONSTRAINT fk_user_pid FOREIGN KEY(UserID)REFERENCES Users(UserID)

ALTER TABLE UserCoupons
ADD CONSTRAINT fk_coupon_pid FOREIGN KEY(CouponID) REFERENCES Coupon(CouponID)